[Boost-users] Seeking in a serialized file

Subject: [Boost-users] Seeking in a serialized file
From: gnu indian (gnuindian_at_[hidden])
Date: 2012-02-20 08:37:52

hi,
I am fairly new to boost and using it for serialization. Though I went through the archives, couldn't get a clear answer to the following:

How do I fseek in a file and load from an offset. I don't want to read the whole data in the file; which works ( as given in some tutorial); but normal fseekg and then loading apparently doesn't work. 
Here is the sample code:

 const char* fileName = "xyz.txt";

  // Create some objects
  const Obj o1(1, false);
  const Obj o2;
  const Obj o3(2, true);
  const Obj* const p1 = &o1;
  int p = 0;
  int q = 0;

  // Save data
  {
    // Create an output archive
    std::fstream ofs(fileName);

    boost::archive::binary_oarchive ar(ofs,boost::archive::no_header);
    // Write data
    ar & o1 & o2 & o3 & p1;
    p = ofs.tellp();
    ar & o1 & o2 & o3 & p1;
  }

  // Restore data
  Obj restored_o1;
  Obj restored_o2;
  Obj restored_o3;
  Obj* restored_p1;
  {
    // Create and input archive
    std::ifstream ifs(fileName);
    boost::archive::binary_iarchive ar(ifs, boost::archive::no_header
    ifs.seekg(p);
    ar & restored_o1 & restored_o2 & restored_o3 & restored_p1;
  }

Mridul